2,463 research outputs found
Equilibrium tuned by a magnetic field in phase separated manganite
We present magnetic and transport measurements on La5/8-yPryCa3/8MnO3 with y
= 0.3, a manganite compound exhibiting intrinsic multiphase coexistence of
sub-micrometric ferromagnetic and antiferromagnetic charge ordered regions.
Time relaxation effects between 60 and 120K, and the obtained magnetic and
resistive viscosities, unveils the dynamic nature of the phase separated state.
An experimental procedure based on the derivative of the time relaxation after
the application and removal of a magnetic field enables the determination of
the otherwise unreachable equilibrium state of the phase separated system. With
this procedure the equilibrium phase fraction for zero field as a function of
temperature is obtained. The presented results allow a correlation between the
distance of the system to the equilibrium state and its relaxation behavior.Comment: 13 pages, 5 figures. Submited to Journal of Physics: Condensed Matte
Witness-based Approach for Scaling Distributed Ledgers to Massive IoT Scenarios
Distributed Ledger Technologies (DLTs) are playing a major role in building
security and trust in Internet of Things (IoT) systems. However, IoT
deployments with a large number of devices, such as in environment monitoring
applications, generate and send massive amounts of data. This would generate
vast number of transactions that must be processed within the distributed
ledger. In this work, we first demonstrate that the Proof of Work (PoW)
blockchain fails to scale in a sizable IoT connectivity infrastructure. To
solve this problem, we present a lightweight distributed ledger scheme to
integrate PoW blockchain into IoT. In our scheme, we classify transactions into
two types: 1) global transactions, which must be processed by global blockchain
nodes and 2) local transactions, which can be processed locally by entities
called witnesses. Performance evaluation demonstrates that our proposed scheme
improves the scalability of integrated blockchain and IoT monitoring systems by
processing a fraction of the transactions, inversely proportional to the number
of witnesses, locally. Hence, reducing the number of global transactions.Comment: 6 pages, 7 figures, conference pape
Predictors of fatigue severity in early systemic sclerosis: a prospective longitudinal study of the GENISOS cohort.
ObjectivesLongitudinal studies examining the baseline predictors of fatigue in SSc have not been reported. Our objectives were to examine the course of fatigue severity over time and to identify baseline clinical, demographic, and psychosocial predictors of sequentially obtained fatigue scores in early SSc. We also examined baseline predictors of change in fatigue severity over time.MethodsWe analyzed 1090 longitudinal Fatigue Severity Scale (FSS) scores belonging to 256 patients who were enrolled in the Genetics versus Environment in Scleroderma Outcomes Study (GENISOS). Predictive significance of baseline variables for sequentially obtained FSS scores was examined with generalized linear mixed models. Predictors of change in FSS over time were examined by adding an interaction term between the baseline variable and time-in-study to the model.ResultsThe patients' mean age was 48.6 years, 47% were Caucasians, and 59% had diffuse cutaneous involvement. The mean disease duration at enrollment was 2.5 years. The FSS was obtained at enrollment and follow-up visits (mean follow-up time = 3.8 years). Average baseline FSS score was 4.7(±0.96). The FSS was relatively stable and did not show a consistent trend for change over time (p = 0.221). In a multivariable model of objective clinical variables, higher Medsger Gastrointestinal (p = 0.006) and Joint (p = 0.024) Severity Indices, and anti-U1-RNP antibodies (p = 0.024) were independent predictors of higher FSS. In the final model, ineffective coping skills captured by higher Illness Behavior Questionnaire scores (p<0.001), higher self-reported pain (p = 0.006), and higher Medsger Gastrointestinal Severity Index (p = 0.009) at enrollment were independent predictors of higher longitudinal FSS scores. Baseline DLco % predicted was the only independent variable that significantly predicted a change in FSS scores over time (p = 0.013), with lower DLco levels predicting an increase in FSS over time.ConclusionsThis study identified potentially modifiable clinical and psychological factors that predict longitudinal fatigue severity in early SSc
Synchronization interfaces and overlapping communities in complex networks
We show that a complex network of phase oscillators may display interfaces
between domains (clusters) of synchronized oscillations. The emergence and
dynamics of these interfaces are studied in the general framework of
interacting phase oscillators composed of either dynamical domains (influenced
by different forcing processes), or structural domains (modular networks). The
obtained results allow to give a functional definition of overlapping
structures in modular networks, and suggest a practical method to identify
them. As a result, our algorithm could detect information on both single
overlapping nodes and overlapping clusters.Comment: 5 pages, 4 figure
Trusted Wireless Monitoring based on Blockchain over NB-IoT Connectivity
The data collected from Internet of Things (IoT) devices on various emissions
or pollution, can have a significant economic value for the stakeholders. This
makes it prone to abuse or tampering and brings forward the need to integrate
IoT with a Distributed Ledger Technology (DLT) to collect, store, and protect
the IoT data. However, DLT brings an additional overhead to the frugal IoT
connectivity and symmetrizes the IoT traffic, thus changing the usual
assumption that IoT is uplink-oriented. We have implemented a platform that
integrates DLTs with a monitoring system based on narrowband IoT (NB-IoT). We
evaluate the performance and discuss the tradeoffs in two use cases: data
authorization and real-time monitoring.Comment: 7 pages, 6 figures, Accepted in IEEE Communication Magazin
Q-learning for distributed routing in LEO satellite constellations
End-to-end routing in Low Earth Orbit (LEO) satellite constellations (LSatCs)
is a complex and dynamic problem. The topology, of finite size, is dynamic and
predictable, the traffic from/to Earth and transiting the space segment is
highly imbalanced, and the delay is dominated by the propagation time in
non-congested routes and by the queueing time at Inter-Satellite Links (ISLs)
in congested routes. Traditional routing algorithms depend on excessive
communication with ground or other satellites, and oversimplify the
characterization of the path links towards the destination. We model the
problem as a multi-agent Partially Observable Markov Decision Problem (POMDP)
where the nodes (i.e., the satellites) interact only with nearby nodes. We
propose a distributed Q-learning solution that leverages on the knowledge of
the neighbours and the correlation of the routing decisions of each node. We
compare our results to two centralized algorithms based on the shortest path:
one aiming at using the highest data rate links and a second genie algorithm
that knows the instantaneous queueing delays at all satellites. The results of
our proposal are positive on every front: (1) it experiences delays that are
comparable to the benchmarks in steady-state conditions; (2) it increases the
supported traffic load without congestion; and (3) it can be easily implemented
in a LSatC as it does not depend on the ground segment and minimizes the
signaling overhead among satellites
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